1. Field of the Invention
The present invention is directed to a fiber collimator array and more specifically to a fiber collimator array for use in an optical transmission system and/or an optical sensor system.
2. Technical Background
Collimation is a process by which divergent beams of radiation or particles (e.g., light rays) are converted into parallel beams. Laser diode (LD) collimating lenses are commonly used in laser beam printers, bar code scanners and sensors. In addition, fiber collimators are widely used in a variety of optical applications (e.g., optical filters). Due to the recent increase in demand for fiber collimators, to be used with wave division multiplexed (WDM) systems, reducing the fiber collimator cost has become increasingly important.
However, commercially available fiber collimator arrays have typically implemented separate lenses, which has increased the cost of the array. For example, one commercially available collimator array has utilized a V-groove array substrate with individually aligned gradient-index (GRIN) microlenses and fibers in each V-groove. These GRIN microlenses have generally been produced by an ion-exchange process and normally provide high coupling efficiency and have been utilized as collimators for laser beam printers, bar code scanners, optical isolators, circulators and digital versatile disc (DVD) players, as well as miniature objective lenses for medical/industrial endoscopes.
Planar microlens arrays (PMLAs) are two-dimensional GRIN-type lens arrays that integrate ion-exchange technology and photolithography. By diffusing ions through a photolithographic mask into a glass substrate, numerous microscopic lenses can be formed in various sizes and patterns. Commercially available PMLAs are available with swelled lens surfaces, which tend to increase coupling efficiencies in transceiver applications, or with flat surfaces, which typically simplify collimation with fiber arrays. PMLAs have been used in liquid crystal projectors, three dimensional data processing and two dimensional laser diode (LD) coupling to fibers. Other manufactures, such as Rochester Photonics Corp., have produced aspheric collimating microlenses that are intended to replace GRIN-type microlenses in collimating applications.
However, the effectiveness of GRIN-type PMLAs and collimating arrays incorporating aspheric collimating microlenses are highly dependent on the configuration of the fiber collimator array. As such, it is important to configure the fiber collimator array to reduce insertion loss and internal reflections.
An embodiment of the present invention is directed to an optical fiber collimator array that includes an optical fiber array block and a microlens array substrate. The optical fiber array block includes an angled surface and is configured to receive and retain a plurality of individual optical fibers, which carry optical signals. The microlens array substrate includes a plurality of microlenses integrated along a microlens surface and a sloped surface opposite the microlens surface. The microlens surface is coupled to the angled surface such that the optical signals from the individual optical fibers are each collimated by a different one of the integrated microlenses.
According to another embodiment of the present invention, an optical fiber collimator array includes an optical fiber array block, a microlens array substrate and an index-matched spacer. The optical fiber array block is configured to receive and retain a plurality of individual optical fibers, which carry optical signals. The microlens array substrate includes a plurality of microlenses integrated along a microlens surface and the index-matched spacer couples the optical fiber array block to the microlens array substrate.
Additional features and advantages of the invention will be set forth in the detailed description which follows and will be apparent to those skilled in the art from the description or recognized by practicing the invention as described in the description which follows together with the claims and appended drawings.